In Why Do African and English Clicks Sound So Different? It’s All in Y..., Julie Sedivy says
... Melissa Wright found, after combing through eighteen hours of recorded telephone conversations, that for English speakers, clicks were used for a very different purpose, namely as a conversational signal that the speaker was shifting the topic. You might think of them as the oral equivalent of a paragraph break marking a discontinuity in the conversation.
Wow! I never noticed that.